Commit f4e74030 authored by Fuad Tabba's avatar Fuad Tabba Committed by Paolo Bonzini
Browse files

KVM: arm64: nv: Handle VNCR_EL2-triggered faults backed by guest_memfd 



Handle faults for memslots backed by guest_memfd in arm64 nested
virtualization triggered by VNCR_EL2.

* Introduce is_gmem output parameter to kvm_translate_vncr(), indicating
  whether the faulted memory slot is backed by guest_memfd.

* Dispatch faults backed by guest_memfd to kvm_gmem_get_pfn().

* Update kvm_handle_vncr_abort() to handle potential guest_memfd errors.
  Some of the guest_memfd errors need to be handled by userspace instead
  of attempting to (implicitly) retry by returning to the guest.

Suggested-by: default avatarMarc Zyngier <maz@kernel.org>
Reviewed-by: default avatarMarc Zyngier <maz@kernel.org>
Signed-off-by: default avatarFuad Tabba <tabba@google.com>
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-ID: <20250729225455.670324-20-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent a7b57e09

arch/arm64/kvm/nested.c

+35 −6
Original line number Diff line number Diff line
@@ -1172,8 +1172,9 @@ static u64 read_vncr_el2(struct kvm_vcpu *vcpu) 
	return (u64)sign_extend64(__vcpu_sys_reg(vcpu, VNCR_EL2), 48);

}



static int kvm_translate_vncr(struct kvm_vcpu *vcpu)

static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)

{

	struct kvm_memory_slot *memslot;

	bool write_fault, writable;

	unsigned long mmu_seq;

	struct vncr_tlb *vt;
@@ -1216,9 +1217,24 @@ static int kvm_translate_vncr(struct kvm_vcpu *vcpu) 
	smp_rmb();



	gfn = vt->wr.pa >> PAGE_SHIFT;

	pfn = kvm_faultin_pfn(vcpu, gfn, write_fault, &writable, &page);

	memslot = gfn_to_memslot(vcpu->kvm, gfn);

	if (!memslot)

		return -EFAULT;



	*is_gmem = kvm_slot_has_gmem(memslot);

	if (!*is_gmem) {

		pfn = __kvm_faultin_pfn(memslot, gfn, write_fault ? FOLL_WRITE : 0,

					&writable, &page);

		if (is_error_noslot_pfn(pfn) || (write_fault && !writable))

			return -EFAULT;

	} else {

		ret = kvm_gmem_get_pfn(vcpu->kvm, memslot, gfn, &pfn, &page, NULL);

		if (ret) {

			kvm_prepare_memory_fault_exit(vcpu, vt->wr.pa, PAGE_SIZE,

					      write_fault, false, false);

			return ret;

		}

	}



	scoped_guard(write_lock, &vcpu->kvm->mmu_lock) {

		if (mmu_invalidate_retry(vcpu->kvm, mmu_seq))
@@ -1292,23 +1308,36 @@ int kvm_handle_vncr_abort(struct kvm_vcpu *vcpu) 
	if (esr_fsc_is_permission_fault(esr)) {

		inject_vncr_perm(vcpu);

	} else if (esr_fsc_is_translation_fault(esr)) {

		bool valid;

		bool valid, is_gmem = false;

		int ret;



		scoped_guard(read_lock, &vcpu->kvm->mmu_lock)

			valid = kvm_vncr_tlb_lookup(vcpu);



		if (!valid)

			ret = kvm_translate_vncr(vcpu);

			ret = kvm_translate_vncr(vcpu, &is_gmem);

		else

			ret = -EPERM;



		switch (ret) {

		case -EAGAIN:

		case -ENOMEM:

			/* Let's try again... */

			break;

		case -ENOMEM:

			/*

			 * For guest_memfd, this indicates that it failed to

			 * create a folio to back the memory. Inform userspace.

			 */

			if (is_gmem)

				return 0;

			/* Otherwise, let's try again... */

			break;

		case -EFAULT:

		case -EIO:

		case -EHWPOISON:

			if (is_gmem)

				return 0;

			fallthrough;

		case -EINVAL:

		case -ENOENT:

		case -EACCES: